Ricerc@Sapienza

Shock waves are commonly observed in high-speed flows, and they often interact with the boundary layer close to the wall resulting in localized regions of high wall pressure and wall-heat flux. If the incoming boundary layer is turbulent in nature, it adds to the complexity of the interaction, resulting in an amplified turbulence kinetic energy and turbulent heat flux across the shock, which can significantly alter the flow topology. Additional instabilities developed due to shock/boundary-layer interaction (SBLI) also generate an unsteady motion of the shock wave. Considering, for example, a normal shock observed on an airfoil in transonic regime at two time instances, the significant shock oscillation observed on the suction side (buffet) is associated with a large breathing separation region, resulting in a rapid loss of lift and increase in drag, often hindering the maneuverability of the aerospace vehicle involved. Additional drawbacks of such an uncontrolled interaction include unsteady vortex shedding and shock/vortex interaction, which are the major causes of broadband noise emission. Also, a rapid generation of pressure fluctuations in the interaction region can be detrimental to the structural health of the wing. Such unsteady interactions are not only observed in external flows but also in internal flows such as a thrust generating supersonic nozzle of a rocket engine while operating at sea-level condition. The asymmetric nature of the flow structure and the shock unsteadiness leads to heavy side loads, which pose significant threat to the vehicle structure and its control. The main aim of the proposed project is to numerically simulate and characterize the shock/turbulent boundary layer interaction in a practical geometry of interest, overexpanded supersonic nozzles, using an innovative and efficient active control strategy, i.e. secondary jet, to mitigate the effects of SBLI governed by an optimal feedback mechanism to devise the control parameters.